The present invention relates generally to operations performed and equipment utilized in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides a safety valve which utilizes extension springs in its operation.
It is known to use a compression spring to bias a safety valve toward its closed position. However, in the quest to provide safety valves which will reliably operate at increased depths in a well, and which have reduced wall thicknesses to permit increased flow areas therethrough, some limitations of compression springs make these goals difficult to attain. For example, one limitation of compression springs is that they expand when they are compressed, and so additional space must be provided in the wall thickness of a safety valve to allow for this expansion.
Therefore, it may be seen that valves, such as safety valves, could benefit from improved methods of operation. These methods could use other types of biasing devices to replace or supplement the biasing forces produced by compression springs. Such improvements could be useful in other applications, as well.